Human digestion and detoxification is an inherently inefficient process. This is especially the case for those of us who engage in hard physical training. If you do not consume faecal contents, you may well be allowing some of the most vital health-promoting and anabolic compounds from your food
to be flushed down the toilet.
Certain fruits/berries carry a sour/bitter taste, which serves the evolutionary purpose of deterring predators. These same foods are often very rich in health-promoting phytonutrients and bioactive compounds. Faeces presents a similar situation; the potent odour is a deterrent to consumption, yet this is the result of products derived from colonic microbiotic metabolism. These micro-organisms in your gut produce health-promoting compounds such as short-chain fatty acids, along with the
odorants that give faeces its distinctive smell.
Along with this, for those of us that eat a nutrient-dense diet, there are certain nutrients that have metabolites which confer even greater health benefits than the nutrients themselves. However, these often exit the body following their first round of metabolism, whereas when consumed again (i.e. via faeces), their time in circulation increases, allowing for greater net health effects.
Well, if faeces is actually healthful, why have we been led to believe otherwise?
You see, historically, the goal of nutrition has been quite basic: prevent deficiencies of vital nutrients, and get enough overall energy to survive. However, nowadays, we have an entirely different goal; to live long and well.
Various non-essential nutrients are now considered to serve the purpose of promoting longevity, and more specifically, the preservation of one's quality of life into later decades in life. This includes polyphenolic compounds, along with many non-essential nutrients and metabolites found in faeces. These serve a strong health-promoting purpose for us moderns, but would not have been useful for our ancestors.
Additionally, our ancestors also would have had a much greater burden of morbidity and mortality from infectious disease. Many infectious diseases can be transmitted via the faecal-oral route, but this risk is no longer significant due to the development of antibiotics, strict standards of food production, and sensitive diagnostic tests for infectious agents in the community.
With all that said, I am, of course, completely making all of this up. I wrote this to demonstrate that arguments can be made for virtually any health intervention.
Eating your own faeces sounds absurd, but you may have found yourself thinking "hmmm, that sounds reasonable" as I walked you through that argument.
Such arguments are often propagated for interventions less absurd, but often harmful, so please be weary of the BS you read on the internet!